Suzanne Askar, right, rests her head on the shoulder of Safam Mahate, a student at North Carolina State University, as they stand next to Nida Allam, far left, during a vigil for three people who were killed at a condominium near UNC-Chapel Hill, Wednesday, Feb. 11, 2015, in Chapel Hill, N.C. (AP Photo/ Al Drago)

RALEIGH, N.C. (AP) — The FBI says it is conducting a parallel investigation of the killing of three young Muslims allegedly slain by a neighbor in Chapel Hill, North Carolina.

A self-described “gun toting” atheist with a reputation for bullying his neighbors has been jailed on first-degree murder charges. Police say Craig Stephen Hicks turned himself in.

Police say they Tuesday’s killings may have been over a parking dispute. But they are also investigating whether religious or ethnic hatred motivated Hicks in any way.

Federal investigators say hate crimes haven’t been ruled out. The FBI announced Thursday that it has “opened a parallel preliminary inquiry to determine whether any federal laws were violated.”

More than 5,000 people attended a funeral on Thursday for Deah Shaddy Barakat, his wife, Yusor Mohammad Abu-Salha, and her sister Razan Mohammad Abu-Salha.

The father of the sisters told the AP that he’s certain they were targeted because they are Muslims.